The present invention relates to a method of changing, such as enlarging or reducing, the size of an image reproduced.
In a digital copier and other imaging equipments, a change in magnification has customarily been effected by operating optics while a scanner scans an imaged surface of a document and the resultant picture data are read on a pixel basis. Although capable of producing quality images by use of simple means, the magnification changing processing which relies on operation of optics as stated is incapable of setting up a wide range of magnifications due to severe space conditions.
Meanwhile, interpolation is well known in the art as a method which varies the magnification of an image by image processing which is based on image data read on a pixel basis. Specifically, interpolation is such that pixel data are thinned out or supplemented according to a predetermined algorithm which involves density levels of surrounding pixels. The interpolation scheme works without any problem so long as the magnification ratio is relatively small. However, where the magnification ratio relatively large, the reliability of data representative of a scanned image becomes poor with the result that the quality of a reproduced image is lowered.
In a digital copier, variable magnification is implemented by controlling a scanner section to one scanning rate and a printer section to another scanning rate. Such a variable magnification scheme, however, requires a special connection between the scanner section and the printer section, failing to win a wide range of applications.